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Mangroves: a natural form of hazard mitigation

Mangroves, a type of tropical evergreen forest growing in the intertidal zones in the tropics and subtropics (32oN and 38oS), consist of tree species well adapted to the regularly changing salinity concentrations and water levels associated with such areas. Mangroves are highly productive ecosystems of high ecological importance. Ostling et al. (2009) describe mangroves and the role they play in ecological processing and natural hazards mitigation.

The special roots of mangroves allow them to anchor themselves in this ever changing environment and therefore serve to slow tidal forces and form an important natural barrier against tropical storms and tsunamis. The presence of mangroves has been shown to increase human survival during cyclones and tsunamis as well as being more effective than alternative natural or artificial barriers (i.e. other types of trees, sand dunes, seawalls, groins etc). Mangroves also provide habitat for shrimp, crocodiles and a nursery ground for fishery stock. Currently these forests are being cleared for various agricultural, forestry and urban uses, such as shrimp aquaculture which has led to the clearing of millions of hectares of mangroves. Without the mangroves, natural fishery stocks are affected which leads to more mangroves being cleared to support more extensive and varied types of aquaculture. In light of the growing realisation of the importance of mangroves, revegetation programmes are underway in Bangladesh, Thailand, Vietnam and Tanzania.